The present invention relates, in general, to flexible covers that are held taut by a frame formed of a plurality of tubes, one end of certain of the tubes being fixed to stationary structure.
Boat covers formed of canvas or other synthetic fabrics are mounted by a framework of pivotally interconnected tubes formed of aluminum or stainless steel. While the tubes are pivotal to allow collapsing of the entire frame to a folded down position exposing the boat passenger compartment, the frame is nevertheless is arranged for one particular upright geometry.
Side curtains are frequently mounted around the Bimini top by interconnecting the side curtains to snaps or zippers mounted on the boat, the Bimini top and/or portions of the side curtains themselves.
As with Bimini tops, it is difficult to apply the proper tension to the side curtains to keep the entire surface area of the side curtains equally tensioned in a taut state. It is also difficult, due to shrinkage of the canvas or synthetic material used to form the side curtains, to stretch the ends of the side curtains sufficiently to allow the snaps or zippers to be easily engaged.
Tensioning devices in the form of telescoping tube ends are provided with interconnecting pins and apertures allow the tube ends to telescopingly expand and retract so as to enable equalization of the tension of the Bimini top. In this manner, uniform tension can be applied to the cover to eliminate sags and wrinkles which could lead to the collection of water on the cover or possible tearing of the top.
However, tensioning devices have not be devised specifically for flexible covers, such as side curtains. Further, the tensioning devices used for Bimini tops provide only a small amount of adjustment and the tube ends must be forcibly extended to align the apertures for insertion of the connecting pin. Thus, it remains a difficult task to initially mount the side curtains on the Bimini top frame as well as to equalize tension across the entire extent of the side curtains.
Another application of a flexible covering mounted on a support frame is an awning. The support frame for an awning can take many configurations depending upon whether the frame is stationary and fixed in geometry or is pivotally attached to a support, such as a building wall, and can be pivoted between collapsed and,extended positions.
Awning support frames include a plurality of interconnected tubular members which are joined at ends by elbows. Ends of the tubular members adjacent to the support wall typically have a threaded connection to a pipe clamp or rod mount to facilitate assembly of the frame. The awning is generally provided with inner flanges having eyelets which allow ties to be used to attach the awning to the support frame members.
It is a time consuming task to attach an awning to a support frame due to the numerous ties which must be employed along the entire periphery of the awning.
Other types of support frames have been provided with tensioning means in the form of a turn buckle with opposed threaded bores which engage the threaded ends of two frame members or one frame member and a pivotal clevis mounted on a stationary support. Fine threads have been employed in such turn buckles. However, the fine threads have proven to be too small as the fine threads make rotation of the turn buckle hard to rotate thereby making adjustment of the tensioning device difficult.
Thus, it would be desirable to devise a flexible cover support frame having tensioning means which enables changes in the geometry of the frame to allow easy mounting the cover on the frame as well as to equalize tension over the entire surface area of the cover when mounted on the frame. It would also be desirable to provide a flexible cover support frame in which the tensioning means or devices may be easy applied in a retrofit application to existing support frames. It would also be desirable to provide a flexible cover support frame wherein the tensioning devices may be hand operated without the need for tools or extreme amounts of force.
The present invention is a tensioning apparatus for tightening a flexible cover on a frame structure. The present invention is also a flexible cover frame structure including such a tension apparatus. The tensioning apparatus is particularly useful in tightening building awnings as well as side curtains mounted on a frame structure supporting a Bimini top on a marine vessel.
In one aspect of the invention, the tensioning apparatus includes a flexible cover frame assembly having at least one frame member. The frame member has a first end. A second frame member is axially aligned with the first frame member and has a second end. The first and second ends are oppositely threaded.
A tubular sleeve has first and second oppositely threaded bores extending inward from opposite ends. The bores are threadingly engagable with the first and second threaded ends of the frame members for axial adjustment of the first and second frame members relative to each other upon rotation of the tubular sleeve. This enables the combined length of the first and second frame members and the tubular sleeve to be increased to apply tension to one portion of the frame structure for tightening the flexible cover or side curtain mounted to the frame structure or detachment or decreased to simplify the attachment of the flexible cover to or from the frame structure. Subsequent elongation of the frame members moves the side curtains into a fully tightened, taut position without wrinkles.
In one aspect of the invention, the first and second threaded ends in the frame members are formed of stubs having one end fixedly mounted in the frame member and a second threaded end extending axially outward from the frame member.
In an alternate aspect of the invention, a stabilizer rod is fixed to one of the first and second stubs and projects axially thorough a bore in the tubular sleeve and a bore in the opposed stub. The rod remains extended through the tubular sleeve and both of the first and second stubs regardless of the amount of angular rotation of the tubular sleeve and the extended or retracted position of the frame members to add strength to the tensioning device by preventing buckling of the frame members at extending length positions. By preventing buckling, the stabilizer rod also insures that the frame members do not impede easy rotation of the tubular sleeve.
In another aspect, a fastener is threadingly mounted through the tubular sleeve into engagement with the threaded end portion of one of the first and second stubs to lock the tubular sleeve to the stub in a fixed position.
The tensioning device of the present invention provides significant advantages over previously devised flexible cover tensioning devices. First, the tensioning device is simple to rotate thereby enabling the frame structure to be collapsed or extended to simplify the attachment of the side curtains to the frame structure as well as to extend the side curtains to a fully taut condition without wrinkles.
Second, the tensioning device is easily mountable in a retrofit operation to an existing frame structure. At the same time, the present tensioning device can be easily integrated into an original equipment frame structure.
Third, the tensioning device is mountable at any of a number of different positions on the frame structure to insure that all portions of the cover can be fully tightened to a taut position as well as to simply the attachment of the cover to any portion of the frame structure. Finally, the tensioning device is easy to rotate thereby eliminating the need for tools to attach or remove the cover to and from the frame structure.